Section 157. The trustees shall maintain the street railway property in good operating condition. At the expiration of any lease which is not renewed, a transportation area shall return the property to the owners in as good condition as it was when first taken over, ordinary wear and tear to be taken into consideration. All leases shall be subject to a provision that any question of damages shall, within ninety days from the date of expiration of a lease, be submitted to the department, and its decision or award shall be final, it being understood that fluctuations in the value of the property and equipment shall not be taken into consideration.